class DataList{

  private ListNode head = null;

  DataList(){head = null;}

  DataList(Data d){
    head = new ListNode(d);
  }

  void add(Data d){
    ListNode tmp = head;
    head = new ListNode(d);
    head.store(tmp);
    return;
  }

  Data remove(){
    Data r = head.getData();
    head = head.getNext();
    return r;
  }

  public String toString(){
    String r = "";
    ListNode current = head;

    while(current != null){
      r = r + current.toString() + "\n";
      current = current.getNext();
    }
    return r;
  }

}